Conventionally, there have been measured circuit parameters (such as the S parameters) of a device under test (DUT) (refer to a patent document 1 (Japanese Laid-Open Patent Publication (Kokai) No. H11-38054), for example.
Specifically, a signal is transmitted from a signal source to a receiving unit via the DUT. The signal is received by the receiving unit. It is possible to acquire the S parameters and frequency characteristics of the DUT by measuring the signal received by the receiving unit.
On this occasion, measuring system errors are generated in the measurement due to mismatching between a measuring system such as the signal source and the DUT, and the like. These measuring system errors include Ed: error caused by the direction of a bridge, Er: error caused by frequency tracking, and Es: error caused by source matching.
On this occasion, it is possible to correct the errors according to the patent document 1, for example. The correction in this way is referred to as calibration. A brief description will now be given of the calibration. Calibration kits are connected to the signal source to realize three types of states: open, short-circuit, and load (standard load Z0). In these states, a signal reflected from the respective calibration kits is acquired by a bridge to obtain three types of the S parameter corresponding to the three types of state. The three types of variable Ed, Er, and Es are acquired from the three types of the S parameter.
Moreover, the DUT is fixed to a jig (fixture), and the DUT is connected to a measuring system (such as a network analyzer) via the jig. On this occasion, the errors caused by the measuring system (network analyzer) can be calibrated as described above. Moreover, if transmission line characteristics of the jig are proper, only the phase of a signal supplied from the measuring system to the jig changes due to the jig. Therefore, the phase can be calibrated according to the length of a transmission line of the jig.
However, if a high frequency signal is supplied to the DUT, it is difficult to manufacture a jig having a proper transmission line characteristic. The jig thus causes a loss to a signal supplied from the measuring system to the jig. On this occasion, if only the phase is calibrated, the measurement accuracy decreases. It is thus preferable to carry out more precise calibration by measuring the characteristics of the jig.
It is thus an object of the present invention to measure the characteristics of a jig (fixture) used to measure and calculate circuit parameters of a device under test.